Chemiluminescence



United States Patent poration of Maine No Drawing. Filed July 13, 1964, Ser. No. 382,384

16 Claims. (Cl. 204--59) The present invention relates to chemiluminescence. It has been found, pursuant to the instant discovery, that visible chemiluminescent emission may be generated by the reduction of an organic compound. For example, a cation radical of a fluorescent organic compound or a dication of a fluorescent organic compound capable of direct conversion to its corresponding organic fluorescent compound, by taking on at least one electron, is reduced with a sufliciently energetic reductant to produce said fluorescent compound in its singlet excited state and thus provide a visible chemiluminescent emission.

Pursuant to one embodiment of the instant invention, a 1 l0 molar solution of 9,10-dichloro-9,IO-diphenyl- 9,10-dihydroanthracene in anhydrous tetrahydrofuran (THF) is stirred under an inert atmosphere and treated with a solution of 0.1 molar sodium naphthalenide in tetrahydrofuran. A bright blue light is emitted.

The reaction is as follows:

01 Cal-I5 Cl CsH5 Cu s @fi w 2 NtLCl 2 Cl C H5 Cells If desired, one may start with a (1) radical cation (C) prepared by removing one electron from (A), or a (2) dication (E) Calls bee,

(E) prepared by removing two electrons from (A).

3,391,068 Patented July 2, 1968 ice As is obvious from the above, reactant (A) is the covalent compound corresponding to reactant (E); stated differently, (E) is the dissociated, diionized form of (A). In most solvents, such as tetrahydrofuran (THF), dimethylformamide (DMF), and the like, the reactant is in its covalent state (A); in certain solvents, however, such as H and the like, the reactant apparently is dissociated into its diionized state (E).

As is evident from the above specific embodiment, even in solvents where the covalent structure of the reactant predominates, the reactant is effective in the process contemplated herein to produce lightjust as though the reactant were completely ionized.

Generically, the process of the present invention may be described as follows:

wherein n is 1 or 2 and wherein M is the organic residue of an organic radical cation or dication and Y is selected from Cl, 2Cl*, Br, 2Br, I-, 21*, /280 SO; B134, ZBFQ", B(C6H5)4 ZB(CGH5)4 OAC 2OAC O 8collaso c n 2so,c,n,, N03", 2NO3-, 010;, 2c1o.,, Poc1 2POCl O 0 l (CH )2". 20%(0113)? and the like. When (n) is 1, Y is Cl, for example; when (n) is 2, Y is 2Cl-.

[M]+ .Y, wherein (n) is 2, likewise stands for the reactant compound in its non-ionized or covalent state, as shown in the specific embodiment equation in paragraph 2, above, of this specification. Therefore, by dication herein the corresponding covalent compound is also intended.

Numerous organic cation radicals and dications of the type described above are capable of direct conversion to their corresponding organic fluorescent compounds by taking on at least one electron. Typical of these are the cation radicals or dications of fluorescent aromatic polycyclic hydrocarbons, such as 1,4-dimethoxyanthracene, 1-methoxy-9,l0-diphenylanthracene, 1,4-dimethoxy 9,10- diphenylanthracene, 2,3-benzofluoranthrene, anthracene, rubrene, pyrene, coronene, decacyclene, and the like.

Typical reductants within the purview of the instant invention and sufiiciently energetic to provide an amount of energy at least equivalent to the amount of energy required to excite the aforementioned fluorescent compounds to their singlet excited state are Na, K, Li, sodium naphthalenide, sodium diphenyl radical anion, disodium 9,IO-diphenylanthracenide, disodium stilbene, tetrabutylammonium naphthalenide, magnesium naphthalenide, and other organic radical anion reductants. As will be seen hereinafter, an electrolytic cathode may be used as reductant. The energy of an excited state is an easily measured experimental value. The energy difference between a first excited singlet and its corresponding ground state is defined by the frequency of the first absorption band in the ultraviolet or visible spectrum of the ground state species.

The physical energy released by a reaction is also an experimental quantity. The free energy of a reaction of the type given in the specific embodiment described above can be determined with considerable accuracy by polarographic measurements or by other procedures well known to the physical chemist.

Thus, the operable limits of cation radical chemiluminescence are capable of independent measurement and of clear definition in terms of physical characteristics of ion radicals, reductants, and fluorescent products. Conq a 4 sequently, generating chemilummescent emission by re- The following examples further illustrate the present ducing a cation radical or dicatlon of the type conteminvention, all of Which are carried out at ambient templated herein with a reductant sufficiently energetic to perature 1n the presence of an inert organic solvent, provide an amount of energy requlred to produce the essentially as in Example 1, supra:

Example N 0. Organic Cation or Dication Reductant Mole Ratio Solvent III 9,IO-gichloro-t),l0-dipheny1-9,IO-dihydro- Sodium naphthalenide 1:2 THF.

an racene. IV 9,l0-dibromo-9,10diphenyl-9,lO-di- Sodium anthracenide 1:1 1,24ilmethoxyctl1ane.

hydroanthracene. V 9,lO-diacetoxy-Q,l0-diphenyl-9,10-di- Disodium stilbene 2:1 Dioxane.

hydroanthracene. VI 9,10dibenzoyloxy-9,l0-diphenyl-9,l0- Sodium stilbene radical anion 1:2 Dlethylether.

dihydroanthracene. VII Rubrene radical cation perchlorate Tctrabutyl-ammonium anthracenide DMF. VIIL. 9,l0-dichlororubrene Potassium 1' Benzene. IX 9,10-dichloronaphthacene Electrolytic cathode at 2 volts vs. Diethylcther of dlethylene glycol consaturatcd calomel electrode. taim'ng 0.1 molar tetrabutyl ammonium perchlorate. X Pyrene radical cation perchlorate do Do. XL... Coronene radical cation perchl0ratc Sodium diphenyL Do. XII Decacyclenc radical cation perchlorate do Do. XIII 1,4-dimethoxy-9,l0-dichloro-9,l0-dido Z-methylpyrolidinone.

hydroanthracene. XIV 5-phcnylchrysene radical cation pcrchlo- Electrolytic cathode at 2 volts vs. Diethylether of dlethylcne glycol conrate. saturated calomel electrode. taining 0.1 molar tetrabutyl ammonium perchlorate. XV 9,10-diphenylanthracene radical cation do 1,2-dimethoxyethane containing 0.1 nitrate. molar tetrabutyl ammonium nitrate. XVI 9,l0 diphenylanthracene radical cation .do 1,2-dimetl1oxyethanc containing 0.1 para-toluene-sulfonate. molar tetrabutyl ammonium paratoluencsulionate. XVII 9,lO-diphcnylanthraccne radical cation do 1,2-dimethoxyethanc containing 0.1 tetrafiuoroboratc. molar to't-raoctylphosphonium tetrafluoroborate. XVIII 1,2-henzanthracene radical cation per- ..do Diethylether of dlethylene glycol conchlorate. taining 0.1 molar tetrabutyl ammonium perchlorate.

resulting organic fluorescent compound corresponding to The reactions in the above table produce a visible the organic cation radical or dication in its singlet excited chemiluminescent emission. While only several solvents state can be accomplished by first recognizing the physical are employed, it should be borne in mind that any suit characteristics of the organic cation radical or dication, able inert organic solvent may be employed. Typical as well as the physical characteristics of the reductant solvents are 1,2-dimethoxyethane, tetrahydrofuran, dito be used. If the reductant is sufficiently energetic and methylformamide, dioxane, dimethylether of ethylene the total amount of energy (say, in kilocalories) result- 40 glycol, Z-methylpyrrolidinone, tetramethyl urea, triethyl ing from the reaction with the cation radical or dication phosphate, and the like. Obviously, numerous other suitis enough to produce the corresponding organic fluoresable inert organic solvents and mixtures of any of these cent compound in its singlet excited state (defined above), Will be apparent to the skilled chemist. visible light is produced. Clearly, the instant discovery encompasses numerous The temperature at which the organic cation or dicatmodifications Within the skill of the art. Consequently, ion radical is reduced is not critical, since very excellent While the present invention has been described in detail results have been achieved at ambient temperatures. Prefwith respect to specific embodiments thereof, it is not erably, also, the process of the present invention is carintended that these details be construed as limitations ried out in an inert atmosphere, e.g., nitrogen, helium, upon the scope of the invention, except insofar as they or the like. appear in the appended claims.

Obviously, the present invention has numerous appli- What is claimed is: cations. For example, chemiluminescence of the type 1. A method of generating a visible chemiluminescent realized herein may be used in safety equipment for emission which comprises reducing a reactant compound recognition lighting, signaling, etc. selected from the group consisting of a cation radical of The present invention will best be understood by virtue a fluorescent organic compound and a dication of a of the following illustrative examples: fluorescent organic compound, said reactant compound Exam 1 being capable of direct conversion to its corresponding p e I fluorescent orgamc compound by taking on at least one Ten milliliters of a 1X10" molar Solu ion of 9,10- electron, said reduction being carried out with a suffi- P Y -9, f y h in anhyciently energetic reductant to produce the resulting fluodl'ous tetfahydfofuran is surfed at and admiXed rescent organic compound in its singlet excited state and therewith is 20 milliliters of a solution of 0.1 molar sodium naphthalide in tetrahydrofuran under an atmosphere of nitrogen. A bright blue light is emitted.

thus provide a visible chemiluminescent emission.

2. The method of claim 1 wherein the reactant compound is the cation radical of a fluorescent aromatic poly- Example II cyclic hydrocarbon.

One hundred milliliters of a solution of 10' molar i claim 1 wherein the reactant rubrene radical cation perchlorate (prepared by e1ectr0 pound is the dicatlon of a fluorescent aromatic polycyclic lytic oxidation of rubrene at a platinum anode at a pohydrocarbon tential of about +1 volt vs. the saturated calomel elec- The method of clalm 1 Whcfeln the c ant Comtrode) in dimethylformamide containing 0.1 molar tetra- Pound is p y 9,10 dihydman' butylammonium perchlorate is reduced at a platinum electhracenetrode at a potential of about -1.8 volts vs. the saturated T me od f cla m 1 wherein the reactant comcalomel electrode. A bright yellow chemiluminescent pound is 9,10-dibrorno-9,10-diphenyl-9,ltl-dihydroanthraemission is observed. cene.

6. The method of claim 1 wherein the reactant is a rubrene radical cation.

7. The method of claim 1 wherein the reactant compound is 9,10-dichlororubrene.

8. The method of claim 1 wherein the reactant compound is a 1,2-benzanthracene radical cation.

9. The method of claim 1 wherein the reducing agent is an alkali metal.

10. The method of claim 1 wherein the reducing agent is a polycyclic aromatic radical anion.

11. The method of claim 1 wherein the reducing agent is sodium naphthalene radical anion.

12. The method of claim 1 wherein the reducing agent is sodium diphenyl radical anion.

13. The method of claim 1 wherein the reducing agent is disodium stilbene.

14. The method of claim 1 wherein the reactant compound is reduced at the cathode of an electrolytic cell through which electric current is passed.

15. The method of claim 2 wherein the reactant compound is reduced at the cathode of an electrolytic cell through which electric current is passed.

16. The method of claim 3 wherein the reactant compound is reduced at the cathode of an electrolytic cell through which electric current is passed.

References Cited UNITED STATES PATENTS 5/ 1947 Lacey et a1. 218-8.'3

8/ 1966 Winberg 252-1883 JOHN H. MACK, Primary Examiner.

H. M. FLOURNOY, Assistant Examiner. 

1. A METHOD OF GENERATING A VISIBLE CHEMILUMINESCENT EMISSION WHICH COMPRISES REDUCING A REACTANT COMPOUND SELECTED FROM THE GROUP CONSISTING OF A CATION RADICAL OF A FLUORESCENT ORGANIC COMPOUND AND A DICATION OF A FLUORESCENT ORGANIC COMPOUND, SAID REACTANT COMPOUND BEING CAPABLE OF DIRECT CONVERSION TO ITS CORRESPONDING FLUORESCENT ORGANIC COMPOUND BY TAKING ON AT LEAST ONE ELECTRON, SAID REDUCTION BEING CARRIED OUT WITHA SUFFICIENTLY ENERGETIC REDUCTANT TO PRODUCE THE RESULTING FLUORESCENT ORGANIC COMPOUND IN ITS SINGLET EXCITED STATE AND THUS PROVIDE A VISIBLE CHEMILUMINESCENT EMISSION.
 14. THE METHOD OF CLAIM 1 WHEREIN THE REACTANT COMPOUND IS REDUCED AT THE CATHODE OF AN ELECTROLYTIC CELL THROUGH WHICH ELECTRIC CURRENT IS PASSED. 